Currently submitted to: JMIR Formative Research
Date Submitted: Aug 5, 2026
Open Peer Review Period: Aug 7, 2026 - Oct 2, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
Design and implementation of a prospective birth cohort study to assess immune imprinting, analyzing novel cohort retention strategies
ABSTRACT
Background:
Prospective birth cohorts enable the assessment of the natural history of disease and immune imprinting. Conducting long-term cohort studies is challenging. Clear guidance on how to implement them is necessary.
Objective:
To describe the design and implementation of the IMPRINT cohort study in a semi-rural area of Mexico and to analyze the continuous-improvement techniques used to promote cohort retention and adherence to study procedures.
Methods:
IMPRINT is a prospective cohort study from birth until four years, conducted in Mexico City and Cincinnati. Pregnant women were recruited during their third trimester, and mother-child dyads were enrolled. Weekly RT-PCR testing for influenza and SARS-CoV-2 was conducted on infants' nasal swabs. Positive samples were subtyped and sequenced. Infant and maternal blood and breast milk were collected six weeks after birth, upon detection of influenza or SARS-CoV-2 infection, after influenza vaccination, and at the end of each influenza season for humoral and cellular immune assays. The Plan-Do-Check-Act continuous improvement technique was implemented to address poor adherence to study procedures and cohort retention. The primary outcomes were laboratory-confirmed influenza and SARS-CoV-2 infections.
Results:
Of 1,183 women screened, 799 mother-child dyads were enrolled; 508 had more than one year of child follow-up. Five actions improved weekly nasal swab delivery: including community members as study staff; addressing maternal mental health needs; providing education on breastfeeding and complementary feeding; automatically alerting to non-compliance with >2 weekly nasal swab deliveries; and offering neurodevelopmental assessment to children. Factors associated with poor adherence to study procedures were maternal age ≤25, lack of medical insurance, and low maternal education. Maternal higher educational level and monthly income were associated with cohort retention.
Conclusions:
Implementation of the IMPRINT study in Mexico was challenging but feasible. Clinical research in lower-middle-income countries addresses broad scientific questions while simultaneously identifying needs specific to local communities and improving healthcare access. Clinical Trial: ClinicalTrials.gov ID NCT05436184
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